In general, in the surrounding of a photoreceptor drum in an electrophotographic copying machine, a corona charger, an exposure unit, a developing unit, a copy unit, a charge eraser and a cleaning unit are arranged. The copying machine also comprises transfer unit for transferring the copy paper to the said copy unit and transferring to a fixing unit after copying. Normally, as soon as copying is completed, the above copying machine stops all the operating units including the corona charger and set a waiting condition in order to take account into the life of the photoreceptor drum and the mechanical units. When the next copy operation is performed, a warming up operation of all the operating units including the corona charger is repeatedly performed.
In the above copying machine, a warming up operation before copy operation is performed in order to stabilize the photoreceptor drum, as well as copy operation, wherein in the warming up operation the photoreceptor drum is rotated without copy paper, then feeding and transferring a copy paper is not performed. It takes relatively long time to complete a first copy of an original because the first copy operation is performed after the warming up operation. Particularly, when a lot of original are copied, it takes much time to copy all the original because the warming up operation is performed every time the original is changed.